Olefin disproportionation process

ABSTRACT

A process for converting, by disproportionation, an olefin, particularly an alpha-olefin, to a product containing a mixture of olefins of higher and lower carbon number than at least one of the olefins in the olefin charge, which involves contacting the olefin charge under disproportionation reaction conditions including a temperature from 15*C. to 120*C. with a catalyst composition containing molybdenum, cobalt-molybdenum, tungsten or rhenium on an alumina containing support. The catalyst is initially pretreated with an olefin having two to 10 carbon atoms at a temperature higher than the reaction temperature.

[22] Filed:

United States Patent 1 91 Kobylinski et al.

1 51 Apr. 3, 1973 [54] OLEFIN DISPROPORTIONATION PROCESS [75] Inventors:Tadeusz P. Kobylinski, Cheswick; Harold E. Swift, Gibsonia, both of [73]Assignee: Gulf Research & Development Company, Pittsburgh, Pa.

Mar. 17, 1971 21 Appl. No.: 125,439

UNITED STATES PATENTS Reusser ..260/683 Heckelsberg ..260/683 3,261,8797/1966 Banks ..260/683 Primary Examiner-Delbert E. Gantz AssistantExaminer-C. E. Spresser Attorney-Meyer Neishloss, Deane E. Keith andRichard C. Gaffney [57] ABSTRACT A process for converting, bydisproportionation, an olefin, particularly an alpha-olefin, to aproduct containing a mixture of olefins of higher and lower carbonnumber than at least one of the olefins in the olefin charge, whichinvolves contacting the olefin charge under disproportionation reactionconditions including a temperature from 15C. to 120C. with a catalystcomposition containing molybdenum, cobalt-molybdenum, tungsten orrhenium on an alumina containing support. The catalyst is initiallypretreated with an olefin having two to 10 carbon atoms at a temperaturehigher than the reaction temperature.

10 Claims, No Drawings 1 OLEFIN DISPROPORTIONATION PROCESS Thisinvention relates to an improved process for converting, bydisproportionation, an olefin, particu larly an alpha-olefin, or amixture thereof, to a product containing a mixture of olefins of higherand lower carbon number than at least one of the olefins in the olefincharge stock, which involves contacting the olefin charge with apretreated catalyst composition containing molybdenum,cobalt-molybdenum, tungsten or rhenium on an inert support containingalumina.

The disproportionation reaction involves a process wherein two moleculesof olefin, the same or different, in the presence of a catalyst andunder suitable reaction conditions interact in a manner such that anolefin fragment thereof reacts with another olefinic fragment to produceolefins containing combinations of such olefinic fragments. It isbelieved the carbon atoms of one olefinic double bond form a cyclobutanestructure with the carbon atoms of a second olefinic double bond ofanother molecule and two new olefins are formed by simultaneous ruptureof the carbon atoms of the olefinic double bonds. Thus,disproportionation as defined herein can be illustrated by the followingreaction:

In the equation above, R, R R and R, the same or different, can be analkyl group or hydrogen. By olefinic fragment is meant each of the RCHportions referred to above.

In prior art disproportionation reactions, a major problem resides inpreventing isomerization of the olefinic bond in alpha-olefins tointernal positions when -the charge stock contains at least four carbonatoms,

' tions of alkyl carrying fragments of the olefin charge. In

the case of the preferred alpha-olefins, the main products are ethyleneand an internal olefin having two less carbon atoms that the total ofthe carbon atoms in two molecules of the charge alpha-olefin. Theinhibition of isomerization of the olefin charge stock is achieved byoperating the process at low reaction temperatures using a pretreatedcatalyst comprising molybdenum, cobalt-molybdenum, tungsten or rheniumon a support comprising alumina. The pretreatment comprises contactingthe catalyst with a monoolefinic material having two to carbon atoms permolecule at a temperature higher than the reaction temperature.

The olefin charge stock employed herein comprises any olefin having fromtwo to 30 carbon atoms per molecule so long as at least a portion of thecharge has at least three carbon atoms per molecule. Preferably thecharge stock contains from four to 20 carbon atoms per molecule, andmost preferably the charge stock contains from four to 12 carbon atomsper molecule. The normal alpha-olefins are the preferred olefinic chargestocks in order to reduce the number of products produced. Ethyleneitself cannot be used as a charge stock to the disproportionationreaction since the only product it can produce is itself. A mixture ofethylene and propylene can be employed, however, the

primary disproportionation which will occur will in volve propylenewith'propyle ne to produce butene-Z and ethylene.

Inert diluents can also be present in the olefinic charge stock ifdesired, and such diluents include, for example, paraffins. Theconcentration of the olefinic component in the charge stock is notcritical and is suitably between 5 and 100 percent by weight and ispreferably from 50 to 100 percent by weight.

Examples of suitable olefins which can be utilized as the charge stockfor the subject reaction include catalyst pretreated in accordancewith-the invention under selective reaction conditions. The catalyst iscomposed of molybdenum, cobalt promoted molybdenum, tungsten or rheniumon a support containing alumina. The amount of molybdenum or tungsten,calculated as the metal, on the catalyst is suitably from 1 to 50percent by weight and is preferably from 5 to 20 percent by weight basedon'the total catalyst. The amount of rhenium, calculated as the metal,is suitably from 0.5 to 8 percent by weight of the catalyst, ispreferably from 0.5 to 5 percent and is most preferably from I to 3percent by weight of the catalyst. In the case of the cobalt promotedmolybdenum catalyst, the weight percent cobalt is suitably from 0.1 to5, preferably from 0.5 to 3 percent by weight of the total catalyst.

The support which is suitable for use in the catalyst of this inventionis one containing at least some alumina, usually from 0.002 to weightpercent alumina, and preferably the support contains from 30 to 100weight percent alumina. The most suitable base and most widely used issubstantially pure alumina, A1 0 Known materials, such as silica,thoria, zirconia, etc., can suitably be added to these aluminas, ifdesired.

The catalyst support should suitably possess a high surface area. Bya-high surface area is meant a surface area in excess of about squaremeters per gram. A suitable range of surface area is from 150 to 400square meters per gram, but is usually from about 200 to 320 squaremeters per gram.

The catalyst of this invention can be prepared by any desirableprocedure so long as the metals in the finally prepared catalyst are ina high valence state. Thus, the various components can be mechanicallyground together or the rhenium, for example, can be placed onto analumina catalyst base by sublimation. After the metals are mixedtogether or deposited on the base, they are placed into a high valencestate by a suitable procedure such as by heating with or without thepresence of a gas containing free molecular oxygen. A preferred methodof preparation, however, involves impregnating the catalyst base usingan aqueous solution of a suitable metal salt by techniques familiar tothose in the catalyst preparation arts. Suitable metal salts or saltsolutions include, for example, an aqueous solution of ammoniumparamolybdate; and aqueous solution of cobalt nitrate; rheniumheptoxide; ammonium perrhenate, or an aqueous solution of ammoniummetatungstate. A sufficient amount of a solution of the desired metalsalt is used to introduce the desired amount of rhenium, molybdenum,molybdenum and cobalt, or tungsten, calculated as the metal, on thesupport. The remaining composition is dried, for example, in air at atemperature of about 110 to about 150C. for about 5 to about 24 hoursand is then calcined in air at a temperature of about 400 to about 600C.over a period of about 1 to about 24 hours.

The disproportionation reaction conditions can be varied over a widerange. Thus, the olefin charge, in liquid or gaseous form, can be passedover the catalyst at (1) an LHSV (liquid volume of olefin per volume ofcatalyst per hour) of from about 0.2 to about 60, preferably from 0.5 toabout 10, and most preferably from 1.5 to 5; or (2) a GHSV (gaseousvolume of olefin per volume of catalyst per hour) of from 50 to 1,000 ormore, and preferably from 400 to 700. The reaction temperature issuitably from about 15C. to about 120C, preferably about 75C. to about100C. The pressure is not critical and is desirably low, for example,atmospheric pressure. It is preferred, however, that the pressure besufficient to maintain the feed olefin in the reaction system in theliquid phase in order to obtain increased conversions. Thus, thepressure can be from about 0 pounds to about 600 pounds per square inchgauge, and is preferably from about 0 to about 450 pounds per squareinch gauge. 1f the above procedure is operated in batch, the sameconditions defined above can be used and contact or reaction time can befrom about minutes to about 240 minutes, preferably from about 30minutes to about 120 minutes.

The reaction is preferably carried out in the absence of solvents, butif solvents are used they should not adversely affect the course of thereaction nor react with the components of the reaction system but shouldhave a boiling point sufficiently different from that of any of thecomponents present in the reaction system. Thus, non-polar solvents,such as hexane, cetane, decane, etc., can be used. The amount of solventshould be that amount sufficient to maintain the contents of thereaction system in the liquid phase. Thus, on a volume basis, onevolume'of solvent per volume of reaction mixture can be used.

If the olefin is maintained in the liquid phase, the vaporous products,for example, ethylene, are preferably removed from the reaction zone asmade. At

the end of the reaction period, any vaporous products still present canbe flashed off. The individual components of the reaction product canthen be recovered by any conventional means, such as fractionation.

It is also important that moisture in the reaction system be kept at aminimum. Thus, the catalyst should be flushed with dry nitrogen or otherinert gas to remove air and moisture before the reaction begins. Theflushing gas can suitably be dried by passage through a syntheticzeolite such as molecular sieves. The feed olefin and other materialsadded to the reaction system should similarly be dried by passagethrough a synthetic zeolite such as molecular sieves or otherwise.

The catalyst is then pretreated in accordance with the invention torender the catalyst more selective for the disproportionation reactionand correspondingly less selective for olefin isomerization reaction.Some catalysts, such as aluminas or silica-aluminas, are socalled singlefunctional catalysts in that they are used to promote a single reactionsuch as catalytic cracking or olefin isomerization. This invention isconcerned with multi-functional catalysts as described above which areuseful for reactions such as disproportionation but which also promoteunwanted reactions such as olefin isomerization and polymerization. Thepretreatment in accordance with the invention tends to change themulti-functional catalysts described above to single functionalcatalysts, the single function being disproportionation.

The pretreatment comprises contacting the fresh or freshly regeneratedcatalyst with a monoolefinic hydrocarbon having from two to 10,preferably three to eight carbon atoms at a temperature in excess of themaximum disproportionation reaction temperature, usually a temperaturefrom to 320C., for a time of about 30 seconds to 1 hour. While it is notcertain, it is believed this pretreatment results in the absorption ofthe monoolefin selectively on those catalyst sites responsible forolefin isomerization and polymerization. The adsorbed olefin is thenbelieved to form a non-acidic complex. For reasons which are notunderstood, the pretreatment does not result in .the increased formationof coke. In fact, the pretreatment procedure results in an added benefitin that less coke is formed over a given reaction time period using acatalyst subjected to the pretreatment of this invention. For whatsoeverreasons, the pretreatment method of this invention yields a catalystwhich is unexpectedly improved in the selectivity of the catalyst forthe disproportionation of alpha-olefins and in addition gives less totalcoke on catalyst.

In the pretreatment method, the pretreatment material is a monoolefinhydrocarbon having from two to 10 carbons, preferably from three toeight carbon atoms, per molecule. If the olefin to be disproportionatedhas from two to 10 carbon atoms, then preferably the olefin used for thepretreatment should correspond to the olefin to be disproportionated.The preferred olefins for the catalyst pretreatment method of thisinvention are those having from three to six carbon atoms as theseolefins are particularly effective and are, in addition, more volatileand thus more easily flushed from the catalyst bed after pretreatment.

The olefins are'contacted with the fresh catalyst by passage of theolefins either upflow or downflow through a bed of the catalyst.Generally, the olefins are in the vapor phase under the conditions ofpretreatment. V

The temperature of pretreatment is very important to achieve the desiredresults. The temperature is above the maximum disproportionationreaction temperature. The pretreatment temperature is suitably fromabout 175 to 320C, preferably 190 to 250C.

Any suitable gaseous hourly space velocities of olefin can be used, suchas from 1 to 5,000 volumes of gaseous olefin per volume of catalyst perhour, preferably from 200 to 1,000 GHSV. The olefin is adsorbed veryquickly under the temperatures of pretreatment set forth above, andeffective pretreatment can be results of these runs are shown in Table Ibelow.

achieved in as short a time as 30 seconds to 1 minute,

although times as long as 30 minutes to an hour can be used.

Before the pretreatment-olefin is contacted with the fresh catalyst, thecatalyst is suitably flushed with an inert gas such as nitrogen toremove any free molecular oxygen or water which might be present. Afterpretreatment with an olefin, the catalyst is again preferably flushedwith'an inert gas such as nitrogen to remove any unreacted olefin.

After pretreatment, the disproportionation reaction is run as describedabove for a time until the catalyst is sufficiently deactivated torequire regeneration. The regeneration is by oxidation using methodswell known in the art. The catalyst can be regenerated, for example, byheating the catalyst in the presence of a gas containing free molecularoxygen (suitably from one to 100 percent free molecular oxygen, usuallyfrom two to 25 percent free molecular oxygen) for a time sufficient toremove substantially all of the carbonaceous deposits thereon at atemperature from 400 to 550C. The catalyst is then cooled under an inertgas blanket or flushed to prepare the catalyst for the pretreatmentprocedure of this invention. Suitably and preferably the pretreatmentoccurs as the temperature of the regenerated catalyst cools above forpretreatment.

- The invention will be further described with reference to thefollowing experimental work.

Typical Preparation of a Molybdenum Catalyst An excess amount of anaqueous solution of ammonium paramolybdate was prepared and added to a-40 mesh alumina having a surface area of 380 square meters per gram.The catalyst was separated from the excess solution, dried in an oven at200C. for 6 hours and then calcined at 550C. overnight. Analysis of thecatalyst showed it contained ten percent by weight of molybdenum.

to within the range set forth Table 1 EFFECT OF PRETREATING 10%Mo-ALUMINA CATALYST WITH VARIOUS MATERIALS Reaction Temp. 93C.; l-OcteneFlow Rate 3 LI-ISV; Conditions 20 cc. of catalyst; Reaction Time l-4Hrs. Pretreating Temp. 200C, Flow Rate of Pretreating Conditions Agent500 GHSV (5 LHSV in case of l-Octene); Pretreatment Time 15 minutesverted Referring to Table I, it can be seen that pretreatment of thecatalyst with an olefin having two to eight carbon atoms substantiallyimproves the selectivity of the catalyst for the disproportionation ofl-octene to tetradecene.

A complete analysis of a typical product (that of Example 2 above) isshown in Table 11 below together with an analysis of the product fromExample 6 above where no pretreatment was employed.

TABLE II DISPROPORTIONATION OF l-OCTENE Catalyst: Mo=l0 weight percentAl,0,= weight percent Reaction Conditions: Temperature C.

LHSV 3 l-Butene flow rate SOO GHSV Temperature 200C. Time 15 minutesPretreatment Conditionsz Higher Olefins EXAMPLE 9 Example 2.was repeatedexcept the catalyst was 2 weight percent cobalt and 8 weight percentmolybdenum on alumina. The weight percent conversion of l-octene was46.2 and the weight percent selectivity to tetradecene was'8 8.4.

One added benefit of the pretreatment procedure of this invention is thelowered carbon formation occurring during the disproportionationreaction. This is shown by the data in Table 111 below.

TABLE 111 DlSPROPORTlONATlON OF l-OCTENE Reaction Conditions: 93C.; 3LHSV for l-octene;

reaction time for 2 hours e1 Ex. Pre- Acidity Wt.%

No. Catalyst treatment cc Nl-IJG C. Conv. Select. A|,0 None 10.3 1.27 00 6 Mo-Al O None 14.1 6.83 90.8 28.2 2 Mo-Alfl Yes 9.2 5.2 48.1 89.8Pretreatment Conditions: l-Butene, flow rate 500 GHSV Temp. 200C. Timeminutes EXAMPLE 1 1 TABLE IV DISPROPORTIONATION OF l-OCTENE ReactionConditions: 93C.; 3 Ll-lSV of Loctene;

atmospheric pressure; and

reaction time 6 hours.

Pretreatment with l-butene l-Octene Tetradecene Ex. Time'lemp. Wt Wt.No. C. Min. GHSV Conversion Selectivity 2 200 15 500 48.1 89.8 6 0 90.828.2 12 200 1 500 66.0 50.0 13 200 7.5 500 48.0 89.0 14 200 30 500 40.081.0 15 175 15 500 75.0 45.0 16 260 15 500 41.0 87.0 17 15 500 25.0 72.0

Referring to Table IV, it can be seen that the selectivity isalmostdoubled after only one minute of pretreatment (compare Examples 6and 12) or after 15 minutes at even the low temperature of 93C. (compareExamples 6 and 15 Resort may be had to such variations and modificationsas fall within the spirit of the invention and the scope of the appendedclaims.

We claim:

1. In a process for the disproportion of at least one monoolefin havingfrom three to 30 carbon atoms per molecule or a mixture of at least onemonoolefin having from threeto 30 carbon atoms per molecule withethylene in the presence of a catalyst comprising molybdenum,cobalt-molydenum, tungsten or rhenium on a support consisting ofalumina, the improvement which comprises conducting saiddisproportionation reaction at a temperature from 15 to C. andcontacting said catalyst before said disproportionation reaction with amonoolefinic hydrocarbon having from three to 10 carbon atoms permolecule at a temperature higher than the disproportionation reactiontemperature but less than 320C. for a time of at least 30 seconds.

2. A process according to claim 1 wherein the catalyst comprisesmolybdenum on alumina and the olefin to be disproportionated has fromthree to 30 carbon atoms;

3. A process according to claim 2 wherein the monoolefinic hydrocarbonused to pretreat the catalyst has from three to eight carbon atoms andthe temperature used to pretreat the catalyst is from to 320C. for atime from 30 seconds to one hour.

4. A process in accordance with claim 3 wherein the olefin used topretreat the catalyst is l-butene.

5. A process according to claim 4 wherein the olefin to bedisproportionated is l-octene.

6. A process for the pretreatment of a catalyst consisting of aluminaand at least one metal selected from Mo, W and Re which comprises:

contacting said catalyst with a monoolefinic hydrocarbon having .fromthree to eight carbon atoms per molecule at a temperature higher thanthe disproportionation reaction temperature but less than 320C. for atime of at least 30 seconds and thereafter using said pretreatedcatalyst for the disproportionation of at least one monoolefin havingfrom three to 30 carbon atoms per molecule or a mixture of at least onemonoolefin having from three to 30 carbon atoms per molecule withethylene under disproportionation reaction conditions including atemperature from 15 to 120C. 7. A process for the disproportionation ofat least one monoolefin having from three to 30 carbon atoms permolecule or a mixture of at least one monoolefin having from 3 to 30carbon atoms per molecule with ethylene which comprises:

contacting said olefin with a pretreated catalyst comprising molybdenum,cobalt-molybdenum, tungsten or rhenium on a support consisting ofalumina under disproportionation reaction conditions including atemperature from 15 to 120C, the pretreatment for said pretreatedcatalyst comprising contacting said catalyst with a monoolefinichydrocarbon having from three to 10 carbon atoms per molecule at atemperature from 175 to 320C. for a time of at least 30 seconds;

continuing to contact said olefin to be disproportionated with saidpretreated catalyst for a time sufficient to deactivate said catalyst;

regenerating said catalyst by heating in the presence of a gascontaining free molecular oxygen at a temperature from 400 to 600C.;

flushing said regenerated catalyst with an inert gas;

cooling said regenerated catalyst to a temperature from 175 to 320C.;and

repeating said pretreatment;

flushing said pretreated catalyst with an inert gas;

cooling said pretreated catalyst to a temperature from 15 to 120C.; and

used to pretreat the catalyst is isobutylene.

l0. process according to claim 1 wherein the olefin used to pretreat thecatalyst is l-octene.

2. A process according to claim 1 wherein the catalyst comprisesmolybdenum on alumina and the olefin to be disproportionated has fromthree to 30 carbon atoms.
 3. A process according to claim 2 wherein themonoolefinic hydrocarbon used to pretreat the catalyst has from three toeight carbon atoms and the temperature used to pretreat the catalyst isfrom 175* to 320*C. for a time from 30 seconds to one hour.
 4. A processin accordance with claim 3 wherein the olefin used to pretreat thecatalyst is 1-butene.
 5. A process according to claim 4 wherein theolefin to be disproportionated is 1-octene.
 6. A process for thepretreatment of a catalyst consisting of alumina and at least one metalselected from Mo, W and Re which comprises: contacting said catalystwith a monoolefinic hydrocarbon having from three to eight carbon atomsper molecule at a temperature higher than the disproportionationreaction temperature but less than 320*C. for a time of at least 30seconds and thereafter using said pretreated catalyst for thedisproportionation of at least one monoolefin having from three to 30carbon atoms per molecule or a mixture of at least one monoolefin havingfrom three to 30 carbon atoms per molecule with ethylene underdisproportionation reaction conditions including a temperature from 15*to 120*C.
 7. A process for the disproportionation of at least onemonoolefin having from three to 30 carbon atoms per molecule or amixture of at least one monoolefin having from 3 to 30 carbon atoms permolecule with ethylene which comprises: contacting said olefin with apretreated catalyst comprising molybdenum, cobalt-molybdenum, tungstenor rhenium on a support consisting of alumina under disproportionationreaction conditions including a temperature from 15* to 120*C, thepretreatment for said pretreated catalyst comprising contacting saidcatalyst with a monoolefinic hydrocarbon having from three to 10 carbonatoms per molecule at a temperature from 175* to 320*C. for a time of atleast 30 seconds; continuing to Contact said olefin to bedisproportionated with said pretreated catalyst for a time sufficient todeactivate said catalyst; regenerating said catalyst by heating in thepresence of a gas containing free molecular oxygen at a temperature from400* to 600*C.; flushing said regenerated catalyst with an inert gas;cooling said regenerated catalyst to a temperature from 175* to 320*C.;and repeating said pretreatment; flushing said pretreated catalyst withan inert gas; cooling said pretreated catalyst to a temperature from 15*to 120*C.; and repeating said disproportionation reaction.
 8. A processaccording to claim 7 where the olefin to be disproportionated is1-octene.
 9. A process according to claim 1 wherein the olefin used topretreat the catalyst is isobutylene.
 10. A process according to claim 1wherein the olefin used to pretreat the catalyst is 1-octene.